Use the include output page to show the number 1-PHP Tutorial

The number 1 include. php appears on the output page using include
Echo include 'include _ menu. php ';
?>
Include_menu.php
Echo 'homepage-HTML tutorial-PHP Tutorial ';
?>
There is a number at the end as shown in Figure 1. why?

Reply to discussion (solution)

Remove echo from include. php

Remove echo from include. php

Thank you very much.

Echo include 'include _ menu. php ';
?>

Change
Include 'include _ menu. php ';
?>

Because mongode_menu.php already has echo

What if two echo messages do not return an error?
Or, the reason for one output 1 is that include is successful, so output 1?
Solution

I don't quite understand this principle. is there a Boolean value returned by include? after the file is introduced successfully, true is returned, and then echo becomes 1?

What if two echo messages do not return an error?
Or, the reason for one output 1 is that include is successful, so output 1?
Solution

Your downstairs explanation may answer your questions.